High strength metal bonded tungsten carbide base composites

ABSTRACT

A HIGH STRENGTH AND TOUGH SINTERED TUNGSTEN CARBIDE BASE COMPOSITE CONSISTING ESSENTIALLY OF METAL CARBIDES, CONTAINING TUNGSTEN CARBIDE AS A PRINCIPAL COMPONENT, AND FROM 10 TO 50 WEIGHT PERCENT OF A STEEL BINDER CONSISTING ESSENTIALLY OF 4 TO 30 WEIGHT PERCENT NICKEL AND/OR 1 TO 25 WEIGHT PERCENT COBALT, 1 TO 15 WEIGHT PERCENT MOLYBDENUM AND/OR 1 TO 10 WEIGHT PERCENT CHROMIUM.

HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES Filed Feb. 18, 1971 July 117, 1973 AKIQ HARA ETAL ll Sheets-Sheet l INVENTORS AKIO HARA SYUJI YAZU q. ac e K ATTORNEYS NICKEL PERCENT 0 I0 20 30 4O 5O 6O 7O 8O 90 I00 THE SELECTED IRON-NICKEL DIAGRAM h. mmaEmmnifi O O O m mwmw wmm w z 2 2 m M n M M m u T LfiA J,.1:L1.| I M w w D wrll l lili 1 l W Pal 4! 11!? W W w M H Y W n u 1/ a F.

D 7 .Tl: m m X, M n W G MG? \\\1.\\ 0 0 O m 0 w m m u mmnhkmmmimk July 17, 1973 AKIO HARA ETAL HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES ll Sheets-Sheet (5 Filed Feb. 18, 1971 D m E T m. o m. m A R m T m E m T T N E w I z s B F S C( A w W a 0A AA 0 m a o a a O 0 0 m m 5 4 a w July 17,, 1973 AKIO HARA EFAL 3,746,519

HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES Filed Feb. 18, 1971 ll Sheets-Sheet 4 FIG. 4

EFFECT OF ANNEALING TEMPERATUPE ON HARDNESS OF YOWC-(Fe- Ni) IOO MATRIX COMPOSITION Fe- IBNI-IOCo- 4.8Mo-2Cr Fe-l8Ni-lOC0-6Mo Fe-l4Ni-6Co A- Fa-ZONi HARDNESS CHANGE SliERo 200 300 400 500 600 xlhr ANNEALING TEMPERATURE (C) July 17, 1973 AKIQ HARA ET AL 3,746,519

HIGH STRENGTH METAL. BONDED 'IUNGS'IEN CARUIUI'I HASH (IOMIOSI'IHS Filed Feb: 18, 1971 l1 Sheets-Sheet 5,,

'FIG. 5

v Fe-IGNi-IOCo July 17, 1973 AKIO HARA ETAL 3,746,519

HIGH STRENGTH METAL BONDED TUNCSTEN CARBIDE BASH COMPOSITES Filed Feb. 18, 1971 ll Sheets-Sheet (5.

FIG. 6

July 17, 1973 o HARA ET AL. 3,746,519

HIGH STRENGTH METAL BONDED TUNGSIEN CARBIDE} BASE COMPOSITES Filed Feb. 18, 1971 ll Sheets-Sheet 7 BROKE FIG 8 STRAIN m) 5 0 In (z m 88381.5

O O N July 17, 1973 Am ARA Em. 3,746,519

HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES Filed Feb. 18, 1971 ll Sheets-Sheet 8 FIG. 9

MARTENSITE CONTENT w.)

PLASTIC STRAIN (%)v July 17, 1973 AKIQ HARA EI'AL 3,746,519

HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES Filed Feb. 18, 1971 ll Sheets-Sheet 9 Fe-IGNi-IOCO 0.060 (O.Il5)

CI3C2 M026 FIG.|O

AKIO HARA EI'AL 3,746,519

July 17, 1973 HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES Filed Feb. 18, 1971 11 Sheets-Sheet 10 FIG. ll

July 17, 1973 AKIQ HARA ETAL HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES ll Sheets-Sheet 11 Filed Feb. 18, 1971 FIG. I2

TEST RESULT OF PUNCHES (MADE OF PRESENT INVENTION) DIE(WC-30% CoI WORK MATERIAL Cu'NI ALLOY) PRODUCT LIFE OF THE PUNCH HSSISKHS) 500 PC'S PRESENT INVENTION 45000- 50000 PC'S United States Patent 3,746,519 HIGH STRENGTH METAL BONDED TUNGSTEN CARBIDE BASE COMPOSITES Akio Hara and Syuji Yazu, Hyogo, Japan, assignors to Sumitomo Electric Industries Ltd., Higashi-ku, Osakashi, Japan Filed Feb. 18, 1971, Ser. No. 116,622 Claims priority, application Japan, Feb. 18, 1970, 45/13,399; July 31, 1970, 45/67,646 Int. Cl. B22f 3/00 US. Cl. 29182.7 6 Claims ABSTRACT OF THE DISCLOSURE A high strength and tough sintered tungsten carbide base composite consisting essentially of metal carbides, containing tungsten carbide as a principal component, and from 10 to 50 weight percent of a steel binder consisting essentially of 4 to 30 weight percent nickel and/ or 1 to 25 weight percent cobalt, 1 to weight percent molybdenum and/or 1 to 10 weight percent chromium.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to tungsten carbide base composites having improved strength and toughness and more particularly to tungsten carbide base composites bonded with steel binders consisting essentially of iron-nickel or iron-cobalt alloys having added thereto molybdenum and/ or chromium.

Description of the prior art Generally, sintered tungsten carbide base alloys have been produced by bonding tungsten carbide particles with cobalt as a metal binder.

Iron-bonded tungsten carbide composites tend to form a harmful double carbide of iron and tungsten (W Fe C) as the eta phase through the sintering process, and so the total carbon content of the compact is adjusted to preclude the formation of the eta phase W Fe C by adding a fixed carbon thereto. In the case of a carbon excess, the free carbon precipitates in the sintered tungsten car bide base alloy, which lowers the strength of the sintered tungsten carbide base alloy produced. Therefore, it is difficult to produce high strength and high toughness sintered tungsten carbide base alloys because of the very narrow permitted limit of carbon content in the ironbonded tungsten carbide base alloys, and for this reason, some prior art exists directed toward improving this permitted limit of carbon content in iron-bonded tungsten carbide base alloys.

It is known that the very narrow permitted limit of carbon content in iron-bonded tungsten base alloys can be substantially improved by the substitution of nickel for a portion of the iron metal binder. Specifically, the carbon content can expand in accordance with the increase of the nickel content over about 4 weight percent in the iron-nickel alloys used as the metal binder. Tungsten carbide base alloys bonded with iron-nickel alloys, e.g., a Fe-ZS Ni alloy, are already in commercial base (see R. Kohlermann et al., Die Technik, vol. 11, 1957, pp. 736446).

The primary object of this invention is to provide a high strength and high toughness steel-bonded tungsten carbide base composite having a bonding phase consisting essentially of an iron-nickel or an iron-nickel-cobalt alloy.

SUMMARY OF THE INVENTION This invention provides a high strength and high toughness steel-bonded tungsten carbide base composite where- 3,746,519 Patented July 17, 1973 in molybdenum and/or chromium are employed as binder elements in conjunction with the iron-nickel or iron-nickelcobalt alloys.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS Sintered tungsten carbide base alloys bonded with ironnickel alloys undergo phase transformations by heating as shown in FIG. 1. The relationship between the cooling transformation and the heating transformation is as shown in FIG. 2. Specifically, referring to FIG. 2, a martensite transformation of a Fe-25% Ni alloy occurs at about C. during cooling; and on the other hand, an austenite transformation occurs at about 540 C. during heating. These phase transformations have an important influence upon the heat resistance of a tungsten carbide base alloy bonded with the above-identified 75 Fe-ZS Ni alloy.

From the results which Were obtained in a series of experiments, it was found that the bonded iron-nickel phase in a sintered tungsten carbide alloy shows remarkably different characteristics as compared with those of an ironnickel alloy per se. For example, the saturation magnetization of a sintered 70 WG-30 (Fe-Ni) alloy, in accordance with various nickel contents, were determined as shown in FIG. 3. The saturation magnetization of the 70 WG-30 (Fe-Ni) alloy was increased remarkably by applying a sub-Zero treatment to the 70 WG-30 (Fe-Ni) alloy in liquid nitrogen. Since it has been generally believed that the saturation magnetization is increased in proportion to the oc-iIOIl in the bonding phase; from the above fact, it may be concluded that the bonding phase contains a great deal of 'y-iron therein. This conclusion is remarkably different as compared with the iron-nickel diagram as shown in FIGS. 1 and 2. Namely, from the facts described above, it may be concluded that in the iron-nickel alloy used as the bonding phase in a tungsten carbide alloy, the martensite transformation has been restrained by one cause or another. Because of the fact that the martensite reaction of an iron-nickel alloy is athermal, the one cause may be that the Ms (martensite transformation) temperature is lowered by the effects of the carbon and tungsten diffused in the bonding phase; while another possible cause may be that the martensite reaction is restrained by the etfect of tungsten carbide particles surrounding the iron-nickel alloy used as the metal binder.

Accordingly, it is impossible to produce a WC-(Fe'Ni) alloy having a bonding phase of 1.00 percent martensite structure in an as-sintered condition. The saturation magnetization of a WC-(Fe-N'i) alloy may be effectively increased, under the sintered situation, by adding cobalt to the WC-(Fe-Ni) alloy as shown in FIG. 3, and generally, it is well known that the Ms temperature of ironnickel alloys is elevated by adding cobalt to the alloy; and thus, this fact may be interpreted such that the remaining austenite in the bonding phase is reduced by the effect of the added cobalt.

On the basis of the results of the experiments described above, the present inventors have endeavored to examine the effects of adding certain elements to the iron-nickel alloy used as the metal binder. From the results of these experiments, it has been found that sintered tungsten carbide base alloys having a bonding phase consisting of iron-nickel alloys or iron-nickel-cobalt alloys and having added thereto molybdenum or molybdenum and chromium possess excellent properties.

One advantage is the improvement of the heat-resistance of the sintered tungsten carbide base alloy. The heat-softening resistances of various WC-(Fe-Ni) alloys, WC-(Fe-Ni-Co) alloys and tungsten carbide base alloys containing molybdenum and/or chromium as binder elementstherein (after having applied thereto the aforementioned sub-zero treatment) are shown in FIG. 4 as the percent change in hardness after heating each alloy for one hour, wherein the hardness of each alloy before heating is presumed to be 100. As shown in FIG. 4, the alloys containing molybdenum therein according to the present invention had a superior heat-softening resistance as compared with the alloys having the bonding phases of only an iron-nickel or iron-nickel-cobalt alloy.

Various 70 WC-30 (Fe-16 Ni-lO Co) alloys containing various amounts of molybdenum and chromium were prepared in order to examine the effect of the added molybdenum and chromium. The composition of the respective bonding phases are shown in FIGS. 5 and 6. The transverse rupture strengths and hardnesses of the resulting alloys are shown in FIGS. 5 and 6, respectively, wherein the transverse rupture strength increases in accordance with increases in the molybdenum and chromium content; and especially, in the case of a molybdenum content of from 3 to 12 weight percent, a remarkable effect is recognized. The hardness also increases in accordance with an increase in the molybdenum content as shown in FIG. 6.

The minimum nickel content in the bonding phase of the tungsten carbide base alloys according to the present invention is about 4 weight percent as described above and the Ms temperature of the bonding phase decreases in accordance with the increase of nickel content, and thus the tungsten carbide base alloys according to the present invention, in the sintered condition have a large amount of austenite therein.

The relationship between the 0.2% yield stress of a WC-30 (Fe-Ni-Co-Mo-Cr) alloy and the martensite content therein is as shown in FIG. 7. The martensite content in the WG-30 (Fe-Ni-Co-Mo-Cr) alloy is varied by varying the nickel content therein or by heat-treating the alloy, the martensite content of the WC-3O (Fe-Ni-Co- Mo-Cr) alloys being determined by measuring the saturation magnetization values of the alloys. From the results shown in FIG. 7, it is clear that the 0.2% yield stress of the alloy increases in proportion with the increase of martensite content in the bonding phase of the alloy. Accordingly, the present inventors have concluded that to obtain a high strength steel-bonded tungsten carbide base alloy, a large amount of martensite has to be provided in the bonding phase of the alloy.

30 weight percent from the results of the experiments described above. It seems that the addition of cobalt to the metal binder improves the heat resistance of the iron-nickel bonded tungsten carbide base alloy, but the addition of cobalt over 25 weight percent to the metal binder reduces the strength of the resulting iron-nickel bonded tungsten carbide base alloy.

The stress-strain curves of a WG-30 (Fe-16 Ni-IO Co- 4.7 Mo-2 Cr) alloy, according to the present invention, are shown in FIG. 8. Test pieces with a diameter of 4.5 mm. and a length of 9.0 mm. were employed in this compression test. The Instron universal testing machine was used in the compression test. The test pieces were subjected to the heat treatments as shown in Table 1.

9. The martensite content is determined by measuring the saturation magnetization value of the alloy. From the results shown in FIGS. 8 and 9, it will be understood that the martensite content in the bonding phase of steelbonded tungsten carbide base alloys may be adjusted by heat-treating the steel-bonded tungsten carbide base alloy. The compressive strength of the steel-bonded tungsten carbide base alloy, having a bonding phase containing little martensite, is low; and on the other hand, the elongation of that alloy has a maximum value at about 30 weight percent of the primary martensite content in the bonding phase. The remaining austenite in the bonding phase may be converted to martensite by the strain-induced transformation during deformation as shown in FIG. 9.

From the facts described above, it may be concluded that the steel-bonded tungsten carbide base alloy must have a bonding phase consisting of the coexistent structures of martensite structure and austenite structure and the ratio between the martensite content and austenite content in the bonding phase can be adjusted by applying a heat-treatment t0 the steel-bonded tungsten carbide base alloy or by varying the nickel content in the bonding phase. Namely, the characteristics of the steel-bonded tungsten carbide alloy may be easily varied in accordance with the required use by applying a heat-treatment there.- to or by varying the nickel content in the bonding phase.

The sintered tungsten carbide base alloys of the present invention are useful as punches or header-dies, where a requirement is a high toughness.

In order to compare the characteristics of the alloys of the present invention with those of standard alloys, the characteristics of the tungsten carbide alloys bonded with the steel binders containing molybdenum and/or chromium therein are shown in Table 2.

TABLE 2 Matrix composition comtpressityle 0.2% proof Total Impact s reng stress, strain, value, TRS, H Alloy N 0. Ni 00 Mo Or Fe kgJmmJ kg./m1n. percent kg. mJcni. kgJmm. i

The maximum nickel content in the bonding phase of the sintered tungsten carbide base alloy according to the present invention has been determined to be about The characteristics of the commercial high speed steel and tungsten carbide-cobalt alloys are as shown in Table 3.

TABLE 3 Q82 153? s%3 8535?} 1 3%? TBS, Hardness Material kg./mm. kgJrnm. percent m./cm. kgJmmfi RA 320 83. earn; 222 g; g $53 -$383: I 12a 91a 0190 304 801 9 The alloys according to the present invention have 10 the case of an excess of the bonding phase, the alloy superior properties of strength and toughness as corncannot be produced elfectively because of the deformapared with the commercial high speed steel and known Mon, through the s1ntering process, of the compact. tungsten carbide-cobalt alloys as shown in Tables 2 and 3. The present 1nvention will be further illustrated by The superior heat resistance properties which are one reference to the following non-limiting examples. of the characteristics of the alloys according to the pres- EXAMPLE 1 cut invention allows these alloys to be serviceable as cutting tools and hot-working tools; and also, the heat soften- A mlXtllre was P p wlth the followlng COIIIPOSI- ing resistance properties of these alloys, as shown in FIG.

4 allows the alloys to be serviceable as cold-working tools, Wt. percent such as punches and header dies. WC P 70.0

In order to confirm the heat-resistance of the alloys Carbonyl 9 p w r 20.2 of the present invention, cutting tests were performed un- Carbonyl nlckel P Wder 4.8 der the following conditions: Cobalt Powder 3.0 Work material, 845C (steel, containing 0.45% C) a 1.4 Side rake angle, 15 a e Back rake angle, 6' Carbon The cutting tools were prepared from a 12.7 mm. square was added and the mixture was Subjected to of W030 alloys h bi d Phase wet milling in a ball mill for 72 hours and then comcompositions of which are shown in FIG. 10. pressed to a green Compact under a Pressure of 2 tOnS/ cm. after drying the mixture. The green compact was Cuttmg condltlons' sintered in a vacuum atmosphere of 0.1-0.2 mm. Hg at (1) V275 m/mm' 1400" C. for one hour. After cooling, the sintered body was cut and the surface wrapped using diamond paste and mm/mv' then etched with picric acid to produce a replica for the T=l0 electron microscope. The eletrophotography of the (2) V=32.5 m./min. sintered body is shown in FIG. 11. In the microphotog- 1:1 mm raphy, the lens-shaped patterns of martensite structure f=0.15 rum/rev. were observed in the bonding phase, and so it will be T=10' understood that the bonding phase of the sintered tungsten The maximum wear widths of the clearance faces of 40 carbide base alloy according to the present invention comthe inserts were measured. The results of these measureprises the coexistent structure of martensite structure and ments of maximum wear widths are shown in FIG. 10, austenite structure. wherein the results using cutting condition 2 are shown in The sintered tungsten carbide base alloy according to parentheses (the values given for the respective binder the present invention had mechanical properties as folphase compositions). lows: a compressive strength of 503 kg./mm. a 0.2%

The temperature of the edge of the cutting tools duryield point of 332 kg./mm. a total strain of 7.2%, a ing cutting was measured by the cutting tool-Work thermocharpy impact value of 1.10 kgm./cm. the charpy impact couple method, and the measured temperature of the test being conducted employing specimens with a 4.5 mm. edge of the WG-30 (Fe-l6 Ni-10 Co) alloy tool was square and a 40 mm. span; a transverse rupture strength 200 C. during operation with cutting condition 1 and of 340 kg./mm. the bending test being employed using 400 C. with cutting condition 2. a specimen with a 4 mm. thickness, a 8 mm. width and Molybdenum exhibits a remarkable influence on the a 20 mm span; and a RA hardnes of 87,0, heat resistan e f th y Chromium (1068 I101 fixhibit The practical tests for this sintered tungsten carbide a remarkable influence on the heat resistance of the albase alloy and the prior art high-speed steel were pery but chromium coexisting with molybdenum exhibits formed by a punch as shown in FIG. 12. In the results of the influences as shown in FIG. 10. these tests, the prior art high-speed steel was durable to The tungsten carbide base alloys a or g t the Pr Work 500 pieces, but the sintered tungsten carbide base ent invention can be manufactured by any Wello n alloy according to the present invention was durable to powder metallurgical process. The molybdenum and work 45,00050,000 pieces; that is, the sintered tungsten Chromium in the alloy y be p y in the form of carbide base alloy according to the present invention was metallic molybdenum and chromium or as ferro-alloys about 100 times as durable as compared with the prior thereof. When problems of oxidation occur, these eleart hi h. d steal, ments may be added in the form of their carbides, such as Mo C and Cr C EXAMPLE The basic carbides in the alloy according to the present invention may contain titanium carbide, vanadium g, mlxmre was prepared wlth the followmg composl' carbide, hafnium carbide and/or other metal carbides in addition to tungsten carbide as the principal component. WC Owder percent These additional carbides may be added only up to 30 C 1 d 75 weight percent of the tungsten carbide in the alloy be- P a cause of their tendency of lowering the toughness of the my me e POW er alloy. 0 powder 2,5

The bonding phase in the alloy of the present invention Mozc may be present in an amount of from 10 to 50 weight per- Criic cent. In the case of a bonding phase deficiency, the char- A sintered tungsten carbide base alloy was produced acteristics as described above cannot be achieved, and in from this mixture by the process as shown in Example 1.

The sintered tungsten carbide base alloy according to the present invention had the following mechanical properties: a compressive strength of 555 kg./mm. a 0.2% yield point of 414 kg./mm. a transverse rupture strength of 370 kg./rnm. and a RA hardness of 89.5.

A practical test for this sintered tungsten carbide alloy was performed by means of a cutting tool under the following conditions:

Rake angle: 30 Work material: Ever-hard (trademark) which contains 025 to 0.35 wt. percent C, 0.21 Wt. percent Cu, 1.48

wt. percent Mn and 0.14 wt. percent Mo and 0.24 wt.

percent Si. Cutting conditions:

d=0.05 mm.

This sintered tungsten carbide tool cut the material times as long as the prior art high-speed steel tool; and also a prior art hard metal tool could not cut the material because of a great deal of tipping of the edge of the tool.

EXAMPLE 3 The compositions and mechanical properties of the metal binders employed in Example 3 are as shown in Table 4.

TABLE 4 Matrix composition TRS, Hardness Fe N1 M0 Cr kg./mm. RA

Balance..- 11.0 4.7 301 87.0

Present invendo 16.0 4 7 2.0 306 84.7

tlon.

Standard alloy... Balance--- 11.0 281 84.9 .do 16.0 284 82. 2

sten carbide as the principal component and from 10 to weight percent, based on the weight of the total composition, of a steel binder consisting essentially of steel containing from 4 to 30 weight percent nickel and 0ptionally from 1 to 25 percent weight cobalt and from 1 to 15 weight percent molybdenum and optionally from 1 to 10 Weight percent chromium.

2. The hard sintered tungsten carbide base composite according to claim 1, wherein the binder phase consists of a coexistent martensite and austenite structure.

3. The hard sintered tungsten carbide base composite according to claim 2, wherein the binder phase consists essentially of from 4 to 30 weight percent nickel, from 1 to 25 weight percent cobalt, and at least one member selected from the group consisting of from 1 to 15 weight percent molybdenum and from 1 to 10 weight percent chromium with the balance being substantially iron.

4. The hard sintered tungsten carbide base composite according to claim 3, wherein the metal carbide consists essentially of tungsten carbide only.

5. The hard sintered tungsten carbide base composite according to claim 4, wherein the binder phase consists essentially of from 4 to 25 weight percent nickel, from 1 to 20 percent cobalt, and at least one member selected from the group consisting of from 1 to 10 weight percent molybdenum and from 1 to 5 weight percent chromium with the balance being substantially iron.

6. The hard sintered tungsten carbide base composite according to claim 1 wherein said metal carbides contain at least weight percent tungsten carbide.

References Cited UNITED STATES PATENTS 3,653,982 4/1972 Prill 148-l26 X 3,561,934 2/1971 Steven 29'-182.7 3,450,511 6/1969 Frehn 29-l82.8 3,369,891 2/1968 Tarkan et a1 148126 X 3,109,917 11/1963 Schmidt et al. 29182.7 X 3,053,706 9/1962 Gregory et a1. 148-126- X CARL D. QUARFORTH, Primary Examiner R. E. SCHAFER, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,7 4- ,5 9 Dated {141V ].L 1973 Inventor(s) Akio Harsh at 9.1

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Figure 11 of the drawings shown on the attached sheet should be added to the grant only.

Signed and sealed this-26th day of February 197L (SEAL) Atte st: H I

EDWARD M.FLETCHER,JR. A H DANN Attesting Offi Commissioner of Patents FORM PC4050 (10-6 I uscoMM-oc wan-P69 i .5. GOVERNMENT PRINTING OFFICE I9" 0-80-"1. 

